Listening-key



F. A. STEARN.

LISTENING KEY. APPLICATION FILED OCT. 25, 19:6.

Patented 0011.19, 1920.

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UNITED STATES PATENT OFFICE.

FRANKLIN A. STEARN, OF PATERSON, NEW JERSEY, ASSIGNOR TO WES TERN-ELEC- TRIO COMPANY, INCORPORATED, OF NEW'-YORK, N. Y., A CORPORATION OF NEW YORK.

LISTENING-KEY.

. Specification of Letters Patent. Patented O t 19 192() Application filed October 25, 1916. Serial No. 127,657.

To all whom it may concern:

Be it known that I, FRANKLIN A. STEARN, a citizen of the United States,yresiding at Paterson,'in the county of Passaic and State of New Jersey, have invented certain new and useful Improvements in Listening- Keys, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to improvements in operators listening key clrcuits.

t is the object of this invention to provide means whereby an operator may listen from one cord to another at a high rate of speed.

A feature of the invention is a listening key whose contacts may be operated either manually or electromagnetically.

' It is thought that the invention will be best understood from the following detailed description, reference being had to the accompanying drawing. f v

In the drawing, the answering end of a connecting operators cord circuit is diagrammatically shown at the left, while at the right are shown'similar portions of a second cord at the same'operators position.

Assuming that the position is idle and that a call comes in over the line terminating in jack 1, the operator will be informed of the presence of such call by the lighting of the usual line lamp (not shown). She then inserts plug 2 into jack 1, whereupon a circuit will be completed for relay 3'from ground, winding of relay 8, sleeve contacts of plug 2 and jack 1, to grounded battery, through the winding of the well-known cutoff relay (not shown), Relay 3 completes a circuit from ground, through its armature and front contact, and connecting cord sequence switch contact 4:, winding of power magnet 5 of the connecting cordsequence switch, to grounded battery. The connecting cord sequence switch then moves from position 1 into position 2 under the control of its normal spring 6. p

In position 2 of the connecting cord sequence switch, a circuit is completed from ground, connecting cord sequence switch contact 26 and the lower low resistance winding of relay 7 to grounded battery. Relay 7 attracts its armature which operates to close contacts 8, 9, 10, 11 and 12 and open contacts 13 and 14.

During the actuation of the armature of relay 7, a contact 15 is momentarily closed, but performs no function at this time. The mechanical structure of contact 15 is such that it will be closed momentarily when bar 19 moves to the'left, either upon operation by'attraction of the armature of magnet 7, or by depression of a non-lockingkey 18. The contact 15 will also be closed momentarily when the contacts are released and the bar 19 moves to the right.

The connecting cord sequence switch is moved out of position 2 in the well-known manner, and relay 7 thereupon locksqitself up over a circuit from grounded battery, lower winding of relay 7, upper high .resistance winding of relay 7, contact 12, and resistance 16 to ground. The operators head set is now connected to the tip and ring conductors of plug 2through contacts 8 and 9, and to the talking strands of the cord shown at 0 through contacts 10' and 11.

If now the operator answers a call with the plug 2, associated with-the cord circuit in dicated at 0', a circuit will be completed from grounded battery, lower-low-resistance winding of relay 7, contact 26 ofthe connecting cord sequence switch associated withdisconnects the operators head set from the connecting cord shown at 0.

The coil 16 has a resistance low enough to shunt out the high-resistance locking circuit of magnet 7 but is not sufliciently low .to shunt out the lower operating winding of relay 7', when the contact 15 is closed momentarily by the restoration of magnet 7.

If the operator wishes to listen in again on the cord shown at 0, she depresses key 18, which operates the contacts 8 to 14 in elusive, in the same manner in which they were operated upon attraction of the armature of magnet 7. In this case the high resistance holding circuit of magnet 7' will be shunted out by a path from grounded battery, contact 15, to ground, through resistance 16. The release of magnet 7" disconnects the operators head set from the cord shown at 0'.

WVhat is claimed is:

1. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines including a pair of talking conductors and a plurality of signaling conductors for each link circuit, an operators head set, sets of contacts, one for each link circuit to control the connection of said head set to said link circuits, means to operate said contacts manually, and electromagnetic means controlled by said signaling conductors, to operate said contacts to cause them to connect and disconnect said head set ifrom said link cirouits, and electromagnetic means for maintaining the actuated condition of said contacts upon the establishment of a talking connection.

2. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines, an operators head set, sets of contacts, one for each link circuit to control the connection of said head set to saidlink circuits, means for operating one of said contact sets whenever a line is extended to a link circuit, and electromagnetic means to release a previously operated set of contacts whenever a second set of contacts is operated, said contact sets being arranged for manual and electromagnetic actuation.

3. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines, an operators heat set, sets of contacts, one for each link circuit to control the connection of said head set to said link circuits, means to operate said contact sets manually, electromagneticmeans to operate said contacts, electromagnetic means for holding said contacts in an actuated condition, and means for deenergizing said holding means simultaneously with the actuation of a second set of contacts.

4:. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines, an operators head set, sets of contacts, one for each link circuit to control the connection of said head set to said link circuits, electromagnetic means tor operating said contacts, and means to automatically release a previously operated set of contacts whenever a second set of contacts is operated.

5. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines, an operators head set, sets of contacts, one for each link circuit to control the connec tion of said head set to said link circuits,

electromagnetic means for operating said contacts and maintaining them in actuated condition, and means to automatically release a previously operated set of contacts whenever a second set of contacts is operated.

6. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines, an operators head set, sets of contacts, one for each link circuit to control the connection of said head set to said link circuits, means for operating said contacts, and electromagnetic means to automatically release a previously operated set of contacts whenever a second set of contacts is operated.

7. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines, an operators head set, sets of contacts, one for each link circuitto control the connection of said head set to said link circuits, manual means and electromagnetic means for operating said contacts, and electromagnetic means to automatically release a previously operated set of contacts whenever a second set of contacts is operated.

8. In a telephone exchange system, a plurality of. subscribers lines, a plurality of link circuits for interconnecting said lines, an operators head set, sets of contacts, one for each link circuit to control the connection of said headset to said link circuits, electromagnetic means to operate said contacts to cause them to connect and disconnect said head set from said link circuits, and electromagnetic means to automatically release'a previously. operated set of contacts whenever a second set of contacts is operated.

9. In a telephone exchange system, a plurality of subscribers lines, a plurality of link circuits for interconnecting said lines,

an operators head set, sets of contacts, one

for each link circuit to control the connection of said head set to said link circuits, means to operate said contact sets, electro- .iagnetic means for holding said contacts in an actuated condition, and means for deenergizing said holding means simultaneously with the actuation of a second set of contacts.

11. In a telephone exchange system, a plu-- rality of subscribers lines, a plurality of link circuits for interconnecting said lines, an operators head set, sets 01" contacts, one for each link circuit to control the connection of said head set to said link circuits, 5 means to operate said contact sets, electromagnetic means for holding said contacts in an actuation condition, and both manual and electromagnetic means for deenergizing said holding means simultaneously with the actuation of a second set off-contacts. 10 In Witness whereof, I hereunto subscribe my name this 24th day of October A. D.,

FRANKLIN A. STEARN. 

